This Core will focus on identifying the nature of cells in skin and skeletal muscle after marrow cell transplantation. Donor cells and their specific lineages will be ascertained and colocalized by confocal and deconvolution fluorescent microscopy. Donor cells will be tracked in tissue sections or cell suspensions by expression of GFP, beta-galactosidase or the presence of male DNA. The lineage of identified donor cells will be ascertained by standard morphology, geographical location and immunohistochemistry. A variety of lineage specific antibodies will be employed and are listed in Table 1. Colocalization of donor and lineage markers will be confirmed using confocal or deconvolution fluorescent microscopy. The Core provides high-level expertise for these approaches. Dr Badiavas, one of the co-heads, is an experienced dermatopathologist and Dr. Bearer, the other co-head, is a highly accomplished investigator with a focus on cellular cytoskeleton and is confocal microscopy. They bring tremendous technical skill and will be supported in this Core by two technicians. The Core contains 2 new Zeiss fluorescent motor-driven microscopes, an upright Axioplan 2 and an inverted Axiovert 200M, and a Zeiss 510 confocal laser-scanning microscope capable of four-color imaging. The Core will be capable of standard deconvolution fluorescent microscopy, 3D reconstructions and confocal microscopy These latter, plus photomapping, will be used to simultaneously show a donor marker and a cell type specific marker. The Core will be open to COBRE participants and there will be no charges.